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Ambient Air Exhaust Gas Sampling Points

Time：

2022-07-29

Environmental monitoring is an important tool for assessing the effectiveness of production environmental controls. Sampling is the first step in ambient air monitoring. Let's learn about the technical points of ambient air exhaust gas sampling.

Environmental monitoring is an important tool for assessing the effectiveness of production environmental controls. In order to effectively control and objectively evaluate the environmental quality of the clean area, it should be comprehensively monitored. Sampling is the first step in ambient air monitoring. Then, what are the technical points of ambient air exhaust gas sampling, you can read down!

Ambient Air Sampling

1. General principles of ambient air monitoring network design:
(1) Within the scope of monitoring, sufficient and representative environmental quality information must be provided.
(2) The monitoring network should consider the integrity of the obtained information.
(3) Based on the socio-economic and technical level, analyze the economic benefits according to the purpose of monitoring, and seek an optimized and highly operable monitoring plan.
(4) According to the actual situation of the site, consider other factors affecting the monitoring point.

2. General principles for the layout of ambient air quality monitoring points:
(1) The points should be well representative, and should be able to objectively reflect the air pollution levels and changing laws within a certain spatial range.
(2) It should be considered that the setting conditions of each monitoring point are as consistent as possible, so that the monitoring data obtained by each monitoring point are comparable.
(3) The distribution of monitoring points in each administrative region should be as uniform as possible to reflect its air pollution level and law; at the same time, the layout should also consider the pollution status and changing trends of the city’s main functional areas and major air pollution sources. .
(4) The layout of ambient air monitoring points should be considered in conjunction with urban planning, so that the determined monitoring points can take into account the needs of future development of the city.

3. The meaning of intermittent sampling of ambient air samples:
Refers to the sampling method used to collect an ambient air sample within a certain period of time or within 1 hour to monitor the average concentration of pollutants in the ambient air during the period or hour.

4. Unpowered sampling of ambient air:
A sampling method that directly collects pollutants by exposing the sampling device or gas sample capture medium to the ambient air without the need for pumping power, relying on the natural diffusion, migration, and sedimentation of the pollutant molecules to be measured in the ambient air.

5. When the ambient air is continuously sampled for 24 hours, the composition of the gaseous pollutant sampling system:
The gaseous pollutant sampling system consists of:
sampling head

Sampling header

Sampling branch

induced draft fan

Gas Sample Absorber

and sampler

6. When collecting ambient air samples with plastic bags, the air tightness inspection method:
After sufficient air, seal the air inlet and place it in water without air bubbles.

7. The way to check the air tightness of the newly purchased absorption tube for collecting gas samples:
Fill the absorption tube with an appropriate amount of water, connect it to the water pumping bottle, the water level difference between the two water bottles is 1m, seal the air inlet, and pump air until no air bubbles appear in the absorption tube. After the water surface of the pumping bottle is stable, let it stand for 10 minutes. , the water level of the pumping bottle should not decrease significantly.

8. After sampling the particulate matter in the ambient air, when taking the filter membrane, it is found that the edge contour of the dust on the filter membrane is not clear:
Indicates that there is air leakage during sampling, and this sampling is invalid and needs to be re-sampled.

Fixed Source Exhaust Gas Sampling

1. The meaning of mobile sampling of fixed pollution sources:
A filter cartridge is used to move the sampling at the determined sampling point, and the sampling time of each point is equal, so that the average concentration of the sampling section can be obtained.

2. When the boiler smoke and dust is measured, the blast, induced air and dust removal systems should meet the requirements:
The blast and induced air systems should be complete and work normally, and the adjustment of the damper should be flexible and adjustable. The dust removal system is running normally, no ash blocking, no air leakage, and no wear-resistant paint falling off.

3. The meaning of isokinetic sampling of dynamic pressure balance:
The isokinetic sampling is realized by balancing the differential pressure of the orifice plate installed on the sampling tube with the gas dynamic pressure at the sampling point indicated by the pitot tube.

4. Differences between mobile sampling, fixed-point sampling and intermittent sampling in soot sampling:
Moving sampling: It is to use a filter cartridge to move the sampling on the determined sampling points. The sampling time of each point is equal, and the average concentration of the sampling section is obtained. Fixed-point sampling: It is to take a sample at each measuring point to obtain the average concentration of the sampling section, and to understand the change of particle concentration on the flue section.

Intermittent sampling: It is to sample the emission sources with periodic changes according to the changes of working conditions and their continuation time, and then obtain the time-weighted average concentration.

5. The larger the value of excess air coefficient α, the larger the actual air supply is than the theoretical air amount required for fuel combustion, and the more sufficient the oxygen in the furnace. Is the air coefficient as large as possible, which is more conducive to the combustion of the furnace? Why?
When the excess air coefficient is too large, a large amount of cold air will enter the furnace, and the furnace temperature will drop, which is not good for combustion.

Unorganized Exhaust Gas Sampling

1. What does "standard state dry exhaust" mean?
Moisture-free exhaust gas at a temperature of 273K and a pressure of 101325Pa.

2. In fugitive emission monitoring, when the average wind speed is ≥1lm/s, the reference point should be set
When the average wind speed is greater than or equal to 1m/s, the pollutants discharged from the measured emission source can generally only affect the downwind direction. Therefore, the reference point can be as close as possible to the measured fugitive emission source under the premise of avoiding the influence of nearby pollution sources. Set so that the reference point can better represent the background concentration value of the monitoring point.

3. In fugitive emission monitoring, when the average wind speed is less than 1m/s (including static wind), the reference point should be set
When the average wind speed is less than 1m/s, the pollutants discharged from the tested fugitive emission source will decrease with the wind migration, and the natural diffusion of pollutants will be enhanced.
At this time, when setting the reference point, it is necessary to avoid the influence of other nearby sources, and to set it away from the measured fugitive emission source within the specified sector range.

4. The "Technical Guidelines for Monitoring Air Pollutants' Unorganized Emissions" (HJ/T 55-2000) classifies the suitability of meteorological factors for monitoring of fugitive emissions:
Category a: It is not conducive to the diffusion and dilution of pollutants, and is suitable for unorganized emission monitoring.
Category b: It is less conducive to the diffusion and dilution of pollutants, and is more suitable for unorganized emission monitoring.
Category C: It is conducive to the diffusion and dilution of pollutants, and is less suitable for monitoring fugitive emissions.
Class d: It is very conducive to the diffusion and dilution of pollutants, and is not suitable for unorganized emission monitoring.

5. When setting up monitoring points for unorganized emission at the perimeter of the unit, how to set monitoring points if the permeability of the wall is good or bad.
When the permeability of the perimeter wall of the unit is very good, monitoring points can be set up close to the outside of the wall.
When the permeability of the surrounding wall of the unit is not good, monitoring points can also be set up close to the surrounding wall, but the gas extraction port should be raised to 20-30cm above the surrounding wall; In the eddy current area, the monitoring point should be set at a distance of 1.5 to 2.0m from the wall and 1.5m from the ground.

6. What are the monitoring projects with significant background values in fugitive emissions? Briefly describe the principles of setting reference points when monitoring fugitive emissions of these projects:
The pollutant items monitored by fugitive emissions are: sulfur dioxide, nitrogen oxides, particulate matter and fluoride.
The principle requirements for setting reference points are:
(1) The reference point should not be affected by the measured fugitive emission sources or as little as possible, and try to avoid the influence of other fugitive emission sources and organized emission sources in its vicinity. Emission sources that have a significant impact on the reference point but have no significant impact on the monitoring point.
(2) The setting of reference points should be based on the principle of the background concentration of pollutants that can represent the monitoring points.